1. Field of the Invention
The invention concerns a roller or a reel spool for winding up a material web, especially of paper.
2. Description of the Related Art
In state-of-the-art spool designs, large roller diameters and bearings, which are positioned at large distances from each other, cause a significant bending of the reel spool core that tends to cause the ends to incline. Such inclination results in a shifting in the layers of the winding material, which causes shiners to develop. The higher marginal pressure in the paper layers creates a bending stress within the winding material, which in turn leads to shear stress between the paper layers that can cause relative shifting. This bending phenomenon thus constitutes the actual dimensioning criterion for such reel spools. As such, the wall thickness and diameter, and consequently weight and cost, of such a reel spool are determined by a relatively small marginal area.
The design of a winding tube known from EP-B-0 500 515 includes a double-walled tube construction with two support bearings. This design affects the bending line of the outer tube in such a way that the outer tube's edge is kept straight or its inclination is minimized. Likewise, a roller described in DE-B-22 11 892 is designed as a 2-body roller. In this design, the inner body is made up of a solid or massive roller core. Here, a straight external mantle tube surface is achieved by giving a conical shape to the core, onto which the tube is pressed as the load increases. At the edge, the tube may be supported hydraulically or pneumatically.
Another type of elastic roll, known from DE-S-23 16 746, for pressure treatment of winding material, envisages a multi-part roller tube/roller core design in which the tube is made of a thermoplastic material. A torsion-resistant but longitudinally movable support of the tube's marginal areas serves to compensate expansion at higher differential temperatures due to different coefficients of thermal expansion. In DE-A-197 29 907, a roller with a 2-body roller core design is described in which the center of the tube is supported by the core, and the wall thickness tapers off toward the edges. The objective here is not to compensate for the global bending of the roller core, but to attain the most constant possible curvature of the roller tube's bending line in order to achieve a spreading effect.
From DE-A-37 03 563, a stretch roller or similar device for paper machine sheets is known and features a double-walled roller design, in which the center of the fiber-reinforced plastic outer tube is supported by the inner metal tube. Here, too, the objective is to achieve a spreading effect, not compensation for the global bending of the inner tube.